Many antenna systems inside modern wireless devices include one or more antenna elements and a ground plane. Often, a ground plane is a portion of conductive material that is large in surface area when compared to the antenna elements. Further, the ground plane is generally connected to various electronic components through their ground connections. An example ground plane use is to complete a monopole antenna, which is fed against the ground plane and acts like a half-wavelength dipole antenna.
Some prior art systems, such as that shown in PCT Publication No. W02003077360, have one or more parasitic elements extending from the ground plane. Those parasitic elements couple with one or more antenna elements so that each parasitic adds its own narrow frequency band when excited. That the parasitic elements are configured to extend from the ground plane is merely a way to ground the parasitics, and the resonant lengths of such parasitics do not include any part of the ground plane. Another prior art use for extensions from ground planes is to provide baluns for differential antenna elements.
While some amount of coupling between antenna elements and the ground plane in a device results in ground plane radiation, no design currently uses the ground plane as a radiating structure in its own right. In fact, ground plane resonance is usually a phenomenon to be minimized. Thus, when engineers design antenna systems for use in devices, they focus on the volume that is reserved for the antenna elements. Therefore, it is generally true that in a given PCB-mounted antenna system, less than half of the volume in the design is utilized for signal radiation.